采用溶胶-凝胶自燃法制备了MnxZn 1-x Cu 0.2 Fe 1.8 O 4 (x=0.5, 0.6, 0.7, 0.8, 0.9)的粉末样品, 并对样品在空气中500℃退火4h. XRD分析表明, 所有的样品都具有单相尖晶石结构, 不同Mn含量样品的平均颗粒尺寸在30～40nm之间. XPS表明: 退火前后, 样品中大部分Mn以Mn 3+ 形式存在; 而Fe则在退火前以Fe 2+和Fe 3+ 混合价态存在, 退火后以Fe 3+ 形式存在. 退火使表层的Mn和Fe所占的百分比都增大. 用VSM常温下磁性的测量, 发现退火样品的矫顽力(HC) 随Mn含量的增加陡峭地增大. 未退火样品的MS随颗粒中Mn含量的增加先增大后减小, x=0.8的样品有最大的MS. 退火对不同Mn含量样品的MS影响不同.
Mn x Zn 1-x Cu 0.2 Fe 1.8 O 4(x=0.5, 0.6, 0.7, 0.8, 0.9) nanoparticles with spinel structure were synthesized by sol-gel auto-combustion method and annealed at 500℃ for 4h in air in order to study the structure and magnetic properties of Mn-Zn-Cu ferrite nanoparticles. The analysis of X-ray diffraction (XRD) shows that all samples are single-phase spinel structure. The particle sizes of samples with different Mn content are estimated from the X-ray spectra to be 30--40nm. X-ray photoelectron spectroscopy (XPS) shows that most of Mn exist in Mn 3+ state before and after annealing, and Fe exist in Fe 3+/2+ mixed states before annealing and in Fe 3+ state after annealing. The annealing leads to the increase of percentages of Mn and Fe in surface layer. The results of vibrating sample magnetometer (VSM) indicate that the coercivities (HC) of samples annealed at 500℃ steeply increase with increasing Mn content. The saturation magnetizations (MS) of unannealed samples with increasing Mn content increase first and then decrease, and the samples (x=0.8) have maximal saturation magnetizations (MS). The influence of annealing on the samples with different Mn content is different.
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